Nonwoven fabric coating containing propylenimine-cross linking agent for carboxyl containing acrylic polymer



United rates Fatent 3,113,038 NQNWQVEN FABRIC COATENG CGNTARNENGPROPYLENIMZNE-CRUSd LHNKENG AGENT FOR CARBQXYL CGNTAINHNG AQRYLHQPGLZMER Charles I. Lattarulo, New York, and Eohn .F. P. Lurzi,

Freeport, N.Y., assignors to later-chemical Corporation, New York,Nfnfl, a corporation of (Elsie No Drawing. Filed liars. 1?, 11961, No.83,611 2 Claims. (Chill-14d) This invention relates to nonwoven fabricsand to a method of making them with a binder comprised of linear acrylicinterpolymers and alkylene imines. Low cost nonwoven fabrics having softhand as well as good fastness to washing and dry cleaning are inconsiderable demand. The attempt to produce such materials is beset bymany problems. Binders are all-important factors in determining theproperties of the finished fabric. At present synthetic rubber latices,particularly butadienestyrene and butadiene-acrylonitrile types, vinyls,acrylates, starch, gum casein and the like constitute the binders inuse. 'Urea and melamine resins are also added to latices in quantitiesup to about of the latex Weight in order to impart thermosettingproperties and to improve Washiastness and solvent resistance. Thesefabrics have found applications in the fields of disposable items,padding and packing, shoe fabrics, interlining for clothing, containers,tapes, toys, filters, vinyl fabric backing, etc. Thus far acceptabilityin the durable outer wear garment field has been less than enthusiasticdue to the lack of nonwoven fabrics having the softness and drapab-ilityof woven goods together with good wet and 'dry cleaning resistance.

There have been many attempts to make such fabrics, chiefly by combiningthermosetting resins with soft polymers in emulsion form in order toobtain a crosslinking effect with consequent improved durability andstrength. The difficulty with these types has been their poordrapability and hand. Generally speaking, as strength and durability wasthus gained, the stiffer the cloth became, and contrariwise, the moreflexible the material, the poorer the tensile strength.

It is the consensus of opinion that significant progress in the field ofnonwoven fabrics will depend almost ontirely on the development of newand better binders.

Of the materials in use, styrene-butadiene binders, although flexibleand elastic, have poor stability to light and poor wet and dry cleaningproperties. Cleaning durability is much better withacrylonitrile-butadiene binders but they discolor, become odonous onaging, and much of the binder mi rates to the surface during bonding,leaving the fabric weak in the center. The latter defect makesdelarnination a common hazard. Starch, gums, casein, and the like impartbrittleness, poor hand, and poor wet strength. The vinyl polymersproduce stilf, tough fabrics suitable for some uses, such as innersoles,shoe interliners, and other applications where a comparatively lowflexibility is acceptable. Acrylic latices otter excellent ligihtstability and good band but their fastness to Wet and dry cleanin is.only fair. The cleaning properties are improved somewhat by combiningthe acrylic latices with minor amounts of urea resins or melamineresins. This recourse, however, has the limitations pointed out above.

3d lhddd ice it has now been discovered that nonwoven fabrics of goodwrashfastness, good dry cleaning fastness, and having excellent hand anddrapaoility can be obtained by using as binders a blend of the laticesof acrylic interpolymers containing a minor amount of carboxyl groupswith a small amount of an alkylene imine, especially propylenimine, inaqueous solution. This is a surprising development. Polyfunctionalimines and various other crosslinking agents have been combined withlatices containing reactive groups, but the crosslinlring; action is atleast understandable in such cases. It now appears that iminesconsidered to be monofunctional produce at least some results hithertoascribed only to poly functional compounds. The explanation for thisphenomenon is not known.

In the examples the parts and percentages are on the weight basis.

Example 1 A binder was made by blending 69 parts of a reactive acryliclatex with 3 parts of an 8.4% aqueous solution of ropylenimine and 37parts of water. The latex was comprised of a linear interpolymer ofZ-ethylhexyl acrylate, 13% acrylonitri-le, and 2% itaconic acid. Thebinder had a pot life of at least 12 days at room temperature.

Example 2 A random web of viscose rayon fibers was passed through thebinder and the excess liquor squeezed out between padding rollers using5 and 10 pounds of pressure. The padded fabric was can dried for 23minutes at 240 F., sufficient for drying and then cured 3 minutes at 360F. The dry pickup amount to 40 to 50% based on the weight of dry fabric.The nonwoven fabric so prepared had notable resistance to alkaline washand solvent. The hand was soft and the drape was good.

The composition of the latex may be varied consider ably withoutseriously impairing the benefits of the novel binder. The monomercontaining the free carboxyl group is effective in the range of fromabout 1 to 6% of the total Weight of monomers. Acrylic acid, methacrylicacid, crotonic acid, isocrotonic acid, and itaconic acid are suitable.The major constituent may be any alkyl ester of acrylic acid, the ralkylgroup having about 1 to 12 carbon atoms. The third ingredient ispreferably acrylonitrile, although latices such as Hycar 1571, acopolymer of 1,3 butadiene:acrylonitrile:methacrylic acid, are operablein the ranges of about 10-20 percent. Propylenimine is preferred as theadditive, although ethylenimine and derivatives of greater carboncontent are operative.

Curing time is not critical. The preferred treatment is given in theexamples. Lower temperatures are effective when the curing time isprolonged, and higher temperatures shorten the time required. Thesevariations in curing schedules are well known in the coating art.

What is claimed is:

1. A nonwoven fabric comprising a web of overlapping intersecting fibersuniformly bonded with a binder formed in situ by reacting a linearacrylic polymer containing a minor amount of carboxyl groups withpropylenimine.

2. A nonwoven fabric comprising a web of overlapping intersecting fibersuniformly bonded with a binder 4- formed in situ by reacting a blend of(A) about 60 parts amounts ranging from about 20 to about 50 weightperby Weight of a latex comprising about 60 parts by Weight cent of filefinislhed fabric. of water and about 40 par Ls by Weight of a dispersion of a linear copoiymer of about 85 parts by weight of Z-ethy l-References flied in the file of 1118 Patent hexyl aoryla'te, about 13parts by weight of acrylonitrile, 5 UNITED STATES PATENTS and about 2parts by weight of itaconic acid, (B) about Q i Q a 0.25 part by Weightof propyien imine, and (C) about 40 am by weight of Water, file binderbeing present in

1. A NONWOVEN FABRIC COMPRISING A WEB OF OVERLAPPING INTERSECTING FIBERSUNIFORMLY BONDED WITH A BINDER FORMED IN SITU BY REACTING A LINEARACRYLIC POLYMER CONTAINING A MINOR AMOUNT OF CARBOXYL GROUPS WITHPROPYLENIMINE.